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In-depth guides
Longer walkthroughs for specific setups: real screenshots, code you can paste and the reason behind every step. The short fix page for each check lives under Learn.
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54 guides, page 1 of 5.
- Security17 min read
"This Connection Is Not Private" in Safari: the fix on iPhone, iPad and Mac
"This Connection Is Not Private" is Safari's warning when a site's certificate fails a check: expired, issued for another name, or from an issuer your device does not trust. Here is the fix on iPhone, iPad and Mac, then how a site owner finds which problem it is.Updated 13 Nov 2026 - Security16 min read
PR_END_OF_FILE_ERROR: what it means and how to fix it
PR_END_OF_FILE_ERROR is Firefox's message when the other end closed the connection before the secure handshake finished. Here is the visitor fix in order of likelihood, then how a site owner proves whose side drops it.Updated 12 Nov 2026 - Security13 min read
SSL_ERROR_RX_RECORD_TOO_LONG: why Firefox says it and how to fix it
SSL_ERROR_RX_RECORD_TOO_LONG is Firefox's error when a server answers an HTTPS request in plain HTTP. Here is the visitor fix, the bytes that make Firefox say "record too long", one curl test that proves it, and the fix for nginx, Apache, app servers and Cloudflare.Updated 11 Nov 2026 - Security16 min read
ERR_SSL_VERSION_OR_CIPHER_MISMATCH: what it means and how to fix it
ERR_SSL_VERSION_OR_CIPHER_MISMATCH means the browser and the server share no TLS version or no cipher, so the handshake stops before any page loads. Here is the visitor fix, then how to tell the two server causes apart and fix each.Updated 10 Nov 2026 - Security20 min read
SSL errors, browser by browser: what each message means and how to fix it
Every SSL error in Chrome, Firefox, Safari and Edge mapped to the server state behind it, with the fix for visitors and for site owners, and a lab where we caused each one on purpose.Updated 9 Nov 2026 - Security13 min read
What is an SSL certificate? Inside the file
An SSL certificate is a signed file that binds your domain name to a public key, issued by an authority browsers trust. Here is everything inside it.Updated 27 Oct 2026 - Security13 min read
What is an SSL handshake? Every step, in plain language
The SSL handshake, today a TLS handshake, is the short exchange in which a browser and a server agree on encryption before any page data moves. Here is each step of the TLS 1.3 exchange, what it costs in milliseconds, and where it breaks.Updated 24 Oct 2026 - Security12 min read
"Your connection is not private": what it means and how to fix it
"Your connection is not private" means the browser rejected the site's certificate: it has expired, covers another name, or comes from an issuer the browser does not trust. Here is the visitor fix, then the site-owner fix for each error code.Updated 4 Oct 2026 - Security11 min read
Access-Control-Allow-Origin: what CORS allows and when * is dangerous
Access-Control-Allow-Origin tells browsers which other sites may read a response. What CORS is, when the * wildcard is fine, when it leaks data, and how to write a safe allowlist.Updated 4 Oct 2026 - Security13 min read
Google Safe Browsing: check your site and clear a flag
Google Safe Browsing is the list behind the red "Deceptive site ahead" warning. Check whether your site is listed, find what triggered it, clean it and request a review.Updated 4 Oct 2026 - Security20 min read
HTTP security headers: what each one does and the set that earns an A
HTTP security headers are instructions your server sends with every page that switch off risky browser defaults. This guide explains each one in plain terms, gives the set that earns an A, and shows how to add them on any server.Updated 4 Oct 2026 - Security12 min read
Pharma and casino spam injections: how they hide and how to find them
Why attackers rent your domain for pharma and casino rankings, the six injection shapes and which report finding shows each, where the code lives in WordPress, and a detection routine for one hour.Updated 4 Oct 2026
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